Story 4.2: Implement full AV replacement with WebRTC stream access

- Update FoundryAdapter to properly detect and expose WebRTC stream access
- Modify ScryingPoolStrip to create video elements with WebRTC streams
- Add video container to roster-strip.hbs template with conditional rendering
- Add CSS to hide Foundry's AV dock (#av and .camera-view)
- Add CSS styling for video containers and elements
- Fix unused variable in FoundryAdapter.buildWebRTCSurface
- Add comprehensive test script for stream access implementation

Architecture: Full replacement mode where module hides Foundry's AV dock
and creates its own video elements using game.webrtc.client.getMediaStreamForUser()

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

styles/scrying-pool.less

@@ -60,3 +60,21 @@
   --sp-badge-surface:                 var(--sp-badge-bg,   rgba(0, 0, 0, 0.72));
   --sp-badge-color:                   var(--sp-badge-text, #dde2e8);
 }
+
+// ============================================================
+// Full AV Replacement Mode: Hide Foundry's AV Dock
+// ============================================================
+// When module is active with stream-access mode, completely hide
+// Foundry's native AV dock UI and replace it with our ScryingPoolStrip
+// This implements the full replacement architecture (not overlay)
+// ============================================================
+
+// Hide the entire AV dock container
+#av {
+  display: none !important;
+}
+
+// Also hide individual camera views in case they're rendered elsewhere
+.camera-view {
+  display: none !important;
+}